Lost Communication With The Diesel Exhaust Fluid (DEF) Control Module

Lost Communication With The Diesel Exhaust Fluid (DEF) Control Module

Circuit Description

The engine control module (ECM), transmission control module (TCM) and diesel exhaust fluid (DEF) control module communicate with a scan tool over the controller area network (CAN) communication bus. The MIMAMORI ECU uses same CAN communication bus circuit during vehicle operations, but it is not used to communicate with a scan tool.

The DEF control module internal main relay is energized to feed the battery voltage to the DEF control module for the system operations when the DEF control module receives an ignition voltage switch ON signal. The DEF control module communication is established during the main relay is energized. When the ignition switch is OFF, the main relay is de-energized after a certain length of time passed. The scan tool communicates with the DEF control module during the main relay is energized.

Circuit/ System Testing Lost Communication with The Diesel Exhaust Fluid (DEF) Control Module